We have demonstrated that in the developing retinal vasculature of the beagle puppy sustained hypercapnia can produce lesions which appear to resemble those seen in RLF. We believe these lesions to be associated with excessive transluminal pressures in developing capillary beds as opposed to being associated with elevated blood oxygen content. Experiments will now be performed to determine if these lesions can also be produced in hypoxic animals. Experiments will also be performed to determine the relationship between genesis of the hypercapnic lesion and the degree of retinal vascular bed maturation at the time of exposure to elevated CO. These studies will include comparison at the electron microscopic level of these lesions to those presumed to be caused by elevated arterial blood content. We will continue to pursue a method for monitoring percent hemoglobin saturation in premature infants by an optical technique. Construction of the necessary contact lens device should be completed, and evaluation on experimental animals will then be undertaken.